Check out [link=http://www.teamkinwald.net]www.teamkinwald.net[/link]. This site is run by professionals in the RC racing industry. This forum is just starting out, but it totally dedicated to the support of the CEN Racing products! By far the best place to be for CEN tips and advice. Not that RC universe is bad, but this site has more specific information about CEN products that you can only find from professionals.

They will provide you with the answers you are looking for if nobody here is able to help.

Sorry, I wish I knew the factory settings of the CEN carb. for you, but it more sounds like your throttle is set too high. Can you find a way to turn down the amount of throttle that the servo is giving the carb? This would not be done with the needles you pointed out in your picture. Instead, you would need to turn the setting down on your transmitter (if the transmitter is capable of this). Or you could try adjusting the servo linkage itself, to enable the carb to be closed more when the servo is at idle. If this all fails, try tightening the screw marked "D" about 1 tick on the clock.

Hope this helps!

Zac